با افزایش جمعیت و رشد شهرنشینی گسترش نواحی سکونتگاهی روند رو به رشدی داشته است. این گسترش سبب افزایش حرکت نقاط جمعیتی به سمت مناطق مخاطرهآمیز ژئومورفولوژیکی شده است که میتواند خطرات زیادی را به همراه داشته باشد. بر این اساس هدف از تحقیق حاضر ارزیابی روند تغییرات نواحی سکونتگاهی شهر مریوان در طی سالهای 1992 تا 2017 و همچنین تعیین میزان توسعه این نواحی به سمت مناطق مخاطرهآمیز ژئومورفولوژی و در نهایت پیشبینی این روند برای سال 2035 میباشد. برای این منظور از تصاویر ماهوارهای سالهای 1992، 2000، 2011 و 2017 استفاده شده است. روش کار به گونهای است که پس از تهیه نقشه نواحی سکونتگاهی سالهای مذکور، با استفاده از مدل LCM توسعه این نواحی برای سال 2035 و میزان حرکت این نواحی به سمت مناطق مخاطرهآمیز ژئومورفولوژیکی پیشبینی شده است. نتایج تحقیق بیانگر این است که وسعت کل نواحی سکونتگاهی از حدود 8/7 کیلومترمربع در سال 1992 به 6/16 کیلومترمربع در سال 2017 افزایش پیدا کرده است و نتایج حاصل از پیشبینی نیز بیانگر این است که این مقدار تا سال 2035 به حدود 3/24 کیلومترمربع خواهد رسید.در طی این سالها در کنار افزایش روند توسعه نواحی سکونتگاهی، حرکت این نواحی به سمت مناطق مخاطرهآمیز نیز افزایش یافته است. به طوری که از مجموعه کل وسعت نواحی سکونتگاهی سال 1992 حدود 7/1 کیلومترمربع در مناطق مخاطرهآمیز ژئومورفولوژیکی قرار داشته که بیشتر شامل مناطق پرشیب و حریم رودخانهها بوده است. در سالهای 2001 و 2011 نیز این روند به 3/2 و 9/2 کیلومترمربع افزایش یافته و همچنین در سال 2017 به میزان 3/3 کیلومترمربع افزایش یافته است.
- . Land Change Modeler
عنوان مقاله [English]
Predicting the trend of urban development toward hazardous areas using multi temporal images (Case Study: Marivan City)
Cities have always been under the influence of various factors and developed under such conditions. Countries around the world are increasingly moving toward urbanization. Physical development of cities occurs in the form of human activities or changes in urban (or rural) land use, and lead to widespread use of lands and adverse environmental effects. In some cases, urban growth leads to environmental hazards and threats human societies. Although the effects of natural factors such as geomorphological phenomena have not been scientifically considered in the development of the study area, there factors had a leading role in this development. Due to geomorphological situation, elevations and steep areas, scattered fault lines and rivers full of water, development of human settlements in the study area faces many constraints. Therefore, it is necessary to plan urban development in the study area based on the geomorphological situation of the region. Accordingly, the present study seeks to evaluate the trend of changes occurred from 1992 to 2017 in the residential districts of Marivan. It also aims to determine the extent of urban growth towards areas facing geomorphological hazards, and finally to predict this trend for 2035.
Materials and Methods
The present study takes advantage of an analytical and statistical research method, along with the necessary software. Moreover, it seeks to study the trend of urban development from 1992 to 2017, and also predict the future trend of development for 2035. Thus, satellite images received in June 1992, 2001, 2011, and 2017 are collected. After preprocessing the images, a land use map is extracted based on the situation of the study area in 1992, 2001. 2011 and 2017. Then, based on these maps and using effective variables, a map is produced based on the predictions made for the residential areas in 2035 by LCM model. Modeling and prediction are performed using LCM model in four steps:
1. Examination of Land Use Changes; 2. Mapping Potential Transfer using Markov Chain. 3. Extracting a predictive map. 4. Evaluating the accuracy of prediction. After predicting and extracting a map of residential areas for each time period, distribution of geomorphologic hazards in these areas is evaluated. In fact, development trend of high risk residential areas has been evaluated.
Discussion and Results
A large part of the study area is mountainous, and these elevations have somehow limited the development of human settlements. Since the present study seeks to determine the trend of human settlements development in areas facing geomorphological hazards, a map has been extracted for these prohibited areas before evaluating the trend of development. These prohibited areas have been mapped in order to identify hazardous areas, and to evaluate development of residential settlements toward these areas. To prepare this map, multiple criteria have been selected based on the situation in the region and experts’ opinion. Then in accordance with the purpose of this research, an information layer was produced using these criteria. Regarding geomorphology, regions with an altitude of more than 1700 m, slopes of more than 30%, north-south direction of the slope, area within 1000 m radii around fault lines and within 200 m radii around rivers are referred to as prohibited areas. After determining prohibited areas, human settlements in the study area were mapped based on 1992, 2001, 2011, and 2017 information. Then, trend of settlement development in prohibited areas was estimated and projected for 2035.
Based on the evaluation of results, there is an increasing demographic trend from 1992 to 2017, so that residential area has increased from 7.8 km in 1992 to 10.9 km in 2017. Maximum development occurred from 2001 to 2011. During this period, settlements developed 3.6 km2 and reached around 14.5 km2 in 2011. From 2011 to 2017, settlements area reached 16.6 km2. Apart from the increasing trend of development in residential areas during these years, this development has mostly occurred toward hazardous areas. So that in 1992, around 1.7 km2 of total residential area was located in prohibited areas, most of which included steeped areas and rivers’ border lines. In 2001 and 2011, this trend has increased from 2.3 to 2.9 km2, and reached 3.3 km2 in 2017. Considering the increasing trend of population toward Marivan, increased constructions in peri-urban and rural areas of Marivan and also along the main road of this city, development of settlements toward prohibited areas has mostly occurred in these areas. According to the main purpose of the present research, development of residential areas is projected for 2035 based on land use in pre-specified years. Results indicate that total area of settlements will increase to about 24.3 km2 in 2035, about 5.7 km2 of which will be in prohibited areas.